The goal of this project is to elucidate basic mechanisms of eukaryotic translation initiation using structural and other biochemical methods. Eukaryotic translation initiation is highly regulated by elements of the untranslated regions of mRNAs, 5'UTR and 3'UTR, by the cellular concentration of initiation factors, by the action of regulatory proteins and by signaling pathways that are initiated by external messages or cellular events. Dysregulation of translation initiation by elevated levels of initiation factors is found in many forms of cancer. Thus, correcting for out-of-balance initiation with small molecule agents is a promising new route for cancer therapy. The proposed research is focused on the mechanisms by which the small ribosomal particle is recruited to mRNA, mediated by the initiation factors eIF4E, eIF4G and the regulatory phosphoprotein 4EBP-1. The second aspect is focused on scanning of the pre-initiation complex to the AUG initiation codon, aided by the interplay between the initiation factors eIF4A, eIF4G and eIF4H. The third topic is on elucidating processes by which the factors eIF1, eIF1A, eIF5 and eIF22 help recruiting the initiator Met-tRNAMet to the ribosome and warrant the correct placement. A significant aspect is to discover and characterize inhibitors of initiation with the goal of developing anti-cancer agents with broad specificity. The research will pursue three specific aims: 1. Define the regulation of eIF4E by tumor-suppressive proteins and small molecules 2. Structure of the eIF4G/eIF4A/eIF4H complex and approaches for inhibition 3. Control of start-codon selection by interactions of eIF5, eIF1, eIF1A and eIF2